/* Respond.js: min/max-width media query polyfill. (c) Scott Jehl. MIT Lic. j.mp/respondjs  */
(function(w) {

	"use strict";

	// exposed namespace
	var respond = {};
	w.respond = respond;

	// define update even in native-mq-supporting browsers, to avoid errors
	respond.update = function() {
	};

	// define ajax obj
	var requestQueue = [], xmlHttp = (function() {
		var xmlhttpmethod = false;
		try {
			xmlhttpmethod = new w.XMLHttpRequest();
		} catch (e) {
			xmlhttpmethod = new w.ActiveXObject("Microsoft.XMLHTTP");
		}
		return function() {
			return xmlhttpmethod;
		};
	})(),

	// tweaked Ajax functions from Quirksmode
	ajax = function(url, callback) {
		var req = xmlHttp();
		if (!req) {
			return;
		}
		req.open("GET", url, true);
		req.onreadystatechange = function() {
			if (req.readyState !== 4 || req.status !== 200
					&& req.status !== 304) {
				return;
			}
			callback(req.responseText);
		};
		if (req.readyState === 4) {
			return;
		}
		req.send(null);
	}, isUnsupportedMediaQuery = function(query) {
		return query.replace(respond.regex.minmaxwh, '').match(
				respond.regex.other);
	};

	// expose for testing
	respond.ajax = ajax;
	respond.queue = requestQueue;
	respond.unsupportedmq = isUnsupportedMediaQuery;
	respond.regex = {
		media : /@media[^\{]+\{([^\{\}]*\{[^\}\{]*\})+/gi,
		keyframes : /@(?:\-(?:o|moz|webkit)\-)?keyframes[^\{]+\{(?:[^\{\}]*\{[^\}\{]*\})+[^\}]*\}/gi,
		// comments: /\/\*[^*]*\*+([^/][^*]*\*+)*\//gi,
		urls : /(url\()['"]?([^\/\)'"][^:\)'"]+)['"]?(\))/g,
		findStyles : /@media *([^\{]+)\{([\S\s]+?)$/,
		only : /(only\s+)?([a-zA-Z]+)\s?/,
		minw : /\(\s*min\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
		maxw : /\(\s*max\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
		minmaxwh : /\(\s*m(in|ax)\-(height|width)\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/gi,
		other : /\([^\)]*\)/g
	};

	// expose media query support flag for external use
	respond.mediaQueriesSupported = w.matchMedia
			&& w.matchMedia("only all") !== null
			&& w.matchMedia("only all").matches;

	// if media queries are supported, exit here
	if (respond.mediaQueriesSupported) {
		return;
	}

	// define vars
	var doc = w.document, docElem = doc.documentElement, mediastyles = [], rules = [], appendedEls = [], parsedSheets = {}, resizeThrottle = 30, head = doc
			.getElementsByTagName("head")[0]
			|| docElem, base = doc.getElementsByTagName("base")[0], links = head
			.getElementsByTagName("link"),

	lastCall, resizeDefer,

	// cached container for 1em value, populated the first time it's needed
	eminpx,

	// returns the value of 1em in pixels
	getEmValue = function() {
		var ret, div = doc.createElement('div'), body = doc.body, originalHTMLFontSize = docElem.style.fontSize, originalBodyFontSize = body
				&& body.style.fontSize, fakeUsed = false;

		div.style.cssText = "position:absolute;font-size:1em;width:1em";

		if (!body) {
			body = fakeUsed = doc.createElement("body");
			body.style.background = "none";
		}

		// 1em in a media query is the value of the default font size of the
		// browser
		// reset docElem and body to ensure the correct value is returned
		docElem.style.fontSize = "100%";
		body.style.fontSize = "100%";

		body.appendChild(div);

		if (fakeUsed) {
			docElem.insertBefore(body, docElem.firstChild);
		}

		ret = div.offsetWidth;

		if (fakeUsed) {
			docElem.removeChild(body);
		} else {
			body.removeChild(div);
		}

		// restore the original values
		docElem.style.fontSize = originalHTMLFontSize;
		if (originalBodyFontSize) {
			body.style.fontSize = originalBodyFontSize;
		}

		// also update eminpx before returning
		ret = eminpx = parseFloat(ret);

		return ret;
	},

	// enable/disable styles
	applyMedia = function(fromResize) {
		var name = "clientWidth", docElemProp = docElem[name], currWidth = doc.compatMode === "CSS1Compat"
				&& docElemProp || doc.body[name] || docElemProp, styleBlocks = {}, lastLink = links[links.length - 1], now = (new Date())
				.getTime();

		// throttle resize calls
		if (fromResize && lastCall && now - lastCall < resizeThrottle) {
			w.clearTimeout(resizeDefer);
			resizeDefer = w.setTimeout(applyMedia, resizeThrottle);
			return;
		} else {
			lastCall = now;
		}

		for ( var i in mediastyles) {
			if (mediastyles.hasOwnProperty(i)) {
				var thisstyle = mediastyles[i], min = thisstyle.minw, max = thisstyle.maxw, minnull = min === null, maxnull = max === null, em = "em";

				if (!!min) {
					min = parseFloat(min)
							* (min.indexOf(em) > -1 ? (eminpx || getEmValue())
									: 1);
				}
				if (!!max) {
					max = parseFloat(max)
							* (max.indexOf(em) > -1 ? (eminpx || getEmValue())
									: 1);
				}

				// if there's no media query at all (the () part), or min or max
				// is not null, and if either is present, they're true
				if (!thisstyle.hasquery || (!minnull || !maxnull)
						&& (minnull || currWidth >= min)
						&& (maxnull || currWidth <= max)) {
					if (!styleBlocks[thisstyle.media]) {
						styleBlocks[thisstyle.media] = [];
					}
					styleBlocks[thisstyle.media].push(rules[thisstyle.rules]);
				}
			}
		}

		// remove any existing respond style element(s)
		for ( var j in appendedEls) {
			if (appendedEls.hasOwnProperty(j)) {
				if (appendedEls[j] && appendedEls[j].parentNode === head) {
					head.removeChild(appendedEls[j]);
				}
			}
		}
		appendedEls.length = 0;

		// inject active styles, grouped by media type
		for ( var k in styleBlocks) {
			if (styleBlocks.hasOwnProperty(k)) {
				var ss = doc.createElement("style"), css = styleBlocks[k]
						.join("\n");

				ss.type = "text/css";
				ss.media = k;

				// originally, ss was appended to a documentFragment and sheets
				// were appended in bulk.
				// this caused crashes in IE in a number of circumstances, such
				// as when the HTML element had a bg image set, so appending
				// beforehand seems best. Thanks to @dvelyk for the initial
				// research on this one!
				head.insertBefore(ss, lastLink.nextSibling);

				if (ss.styleSheet) {
					ss.styleSheet.cssText = css;
				} else {
					ss.appendChild(doc.createTextNode(css));
				}

				// push to appendedEls to track for later removal
				appendedEls.push(ss);
			}
		}
	},
	// find media blocks in css text, convert to style blocks
	translate = function(styles, href, media) {
		var qs = styles.replace(respond.regex.comments, '').replace(
				respond.regex.keyframes, '').match(respond.regex.media), ql = qs
				&& qs.length || 0;

		// try to get CSS path
		href = href.substring(0, href.lastIndexOf("/"));

		var repUrls = function(css) {
			return css.replace(respond.regex.urls, "$1" + href + "$2$3");
		}, useMedia = !ql && media;

		// if path exists, tack on trailing slash
		if (href.length) {
			href += "/";
		}

		// if no internal queries exist, but media attr does, use that
		// note: this currently lacks support for situations where a media attr
		// is specified on a link AND
		// its associated stylesheet has internal CSS media queries.
		// In those cases, the media attribute will currently be ignored.
		if (useMedia) {
			ql = 1;
		}

		for ( var i = 0; i < ql; i++) {
			var fullq, thisq, eachq, eql;

			// media attr
			if (useMedia) {
				fullq = media;
				rules.push(repUrls(styles));
			}
			// parse for styles
			else {
				fullq = qs[i].match(respond.regex.findStyles) && RegExp.$1;
				rules.push(RegExp.$2 && repUrls(RegExp.$2));
			}

			eachq = fullq.split(",");
			eql = eachq.length;

			for ( var j = 0; j < eql; j++) {
				thisq = eachq[j];

				if (isUnsupportedMediaQuery(thisq)) {
					continue;
				}

				mediastyles.push({
					media : thisq.split("(")[0].match(respond.regex.only)
							&& RegExp.$2 || "all",
					rules : rules.length - 1,
					hasquery : thisq.indexOf("(") > -1,
					minw : thisq.match(respond.regex.minw)
							&& parseFloat(RegExp.$1) + (RegExp.$2 || ""),
					maxw : thisq.match(respond.regex.maxw)
							&& parseFloat(RegExp.$1) + (RegExp.$2 || "")
				});
			}
		}

		applyMedia();
	},

	// recurse through request queue, get css text
	makeRequests = function() {
		if (requestQueue.length) {
			var thisRequest = requestQueue.shift();

			ajax(thisRequest.href, function(styles) {
				translate(styles, thisRequest.href, thisRequest.media);
				parsedSheets[thisRequest.href] = true;

				// by wrapping recursive function call in setTimeout
				// we prevent "Stack overflow" error in IE7
				w.setTimeout(function() {
					makeRequests();
				}, 0);
			});
		}
	},

	// loop stylesheets, send text content to translate
	ripCSS = function() {

		for ( var i = 0; i < links.length; i++) {
			var sheet = links[i], href = sheet.href, media = sheet.media, isCSS = sheet.rel
					&& sheet.rel.toLowerCase() === "stylesheet";

			// only links plz and prevent re-parsing
			if (!!href && isCSS && !parsedSheets[href]) {
				// selectivizr exposes css through the rawCssText expando
				if (sheet.styleSheet && sheet.styleSheet.rawCssText) {
					translate(sheet.styleSheet.rawCssText, href, media);
					parsedSheets[href] = true;
				} else {
					if ((!/^([a-zA-Z:]*\/\/)/.test(href) && !base)
							|| href.replace(RegExp.$1, "").split("/")[0] === w.location.host) {
						// IE7 doesn't handle urls that start with '//' for ajax
						// request
						// manually add in the protocol
						if (href.substring(0, 2) === "//") {
							href = w.location.protocol + href;
						}
						requestQueue.push({
							href : href,
							media : media
						});
					}
				}
			}
		}
		makeRequests();
	};

	// translate CSS
	ripCSS();

	// expose update for re-running respond later on
	respond.update = ripCSS;

	// expose getEmValue
	respond.getEmValue = getEmValue;

	// adjust on resize
	function callMedia() {
		applyMedia(true);
	}

	if (w.addEventListener) {
		w.addEventListener("resize", callMedia, false);
	} else if (w.attachEvent) {
		w.attachEvent("onresize", callMedia);
	}
})(this);
